Demonstration of measurement-free universal fault-tolerant quantum computation

Demonstration of measurement-free universal fault-tolerant quantum computation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Demonstration of measurement-free universal fault-tolerant quantum computation Friederike Butt, Ivan Pogorelov, Robert Freund, Alex Steiner, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7092911/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Jan, 2026 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract The ability to perform quantum error correction (QEC) and robust gate operations on encoded qubits opens the door to demonstrations of quantum algorithms. Contemporary QEC schemes typically require mid-circuit measurements with feed-forward control, which are challenging for qubit control, often slow, and susceptible to relatively high error rates. In this work, we propose and experimentally demonstrate a universal toolbox of fault-tolerant logical operations without mid-circuit measurements on a trapped-ion quantum processor. We present modular logical state teleportation between two four-qubit error-detecting codes without measurements during algorithm execution. Moreover, we realize a fault-tolerant universal gate set on an eight-qubit error-detecting code hosting three logical qubits, based on state injection, which can be executed by coherent gate operations only. We apply this toolbox to experimentally realize Grover's quantum search algorithm fault-tolerantly on three logical qubits encoded in eight physical qubits, with the implementation displaying clear identification of the desired solution states. Our work demonstrates the practical feasibility and provides first steps into the largely unexplored direction of measurement-free quantum computation. Physical sciences/Physics/Quantum physics/Quantum information Physical sciences/Physics/Quantum physics/Qubits Full Text Additional Declarations Yes there is potential Competing Interest. Thomas Monz is connected to Alpine Quantum Technologies GmbH, a commercially oriented quantum computing company. The remaining authors declare no competing interests. Cite Share Download PDF Status: Published Journal Publication published 26 Jan, 2026 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7092911","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":499979613,"identity":"9ade3e94-6831-4bc9-a6e8-5d70370a4d33","order_by":0,"name":"Friederike Butt","email":"data:image/png;base64,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","orcid":"https://orcid.org/0009-0007-8954-1274","institution":"Institute for Theoretical Nanoelectronics (PGI-2), Forschungszentrum Jülich, Jülich, Germany","correspondingAuthor":true,"prefix":"","firstName":"Friederike","middleName":"","lastName":"Butt","suffix":""},{"id":499979614,"identity":"8ce672d1-ebc8-438e-82b9-6dd64349a3e5","order_by":1,"name":"Ivan Pogorelov","email":"","orcid":"https://orcid.org/0009-0001-5103-9410","institution":"University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Ivan","middleName":"","lastName":"Pogorelov","suffix":""},{"id":499979615,"identity":"1b8315a0-56d9-4109-b0e0-cedc05f1ac0c","order_by":2,"name":"Robert Freund","email":"","orcid":"https://orcid.org/0009-0007-8401-2322","institution":"University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Robert","middleName":"","lastName":"Freund","suffix":""},{"id":499979616,"identity":"a22e2e84-a119-40d7-ba49-8722c3f40e8b","order_by":3,"name":"Alex Steiner","email":"","orcid":"https://orcid.org/0000-0001-5443-7871","institution":"University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Alex","middleName":"","lastName":"Steiner","suffix":""},{"id":499979617,"identity":"22122a53-6a65-45a2-b3aa-35a24dc8cb5b","order_by":4,"name":"Marcel Meyer","email":"","orcid":"https://orcid.org/0000-0002-7832-5927","institution":"University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Marcel","middleName":"","lastName":"Meyer","suffix":""},{"id":499979618,"identity":"6a4fb233-f7a4-4538-aeb0-0109019c169f","order_by":5,"name":"Thomas Monz","email":"","orcid":"https://orcid.org/0000-0001-7410-4804","institution":"University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Thomas","middleName":"","lastName":"Monz","suffix":""},{"id":499979619,"identity":"f982b315-a802-4d90-822a-c7aece2b37bd","order_by":6,"name":"Markus Müller","email":"","orcid":"","institution":"Institute for Theoretical Nanoelectronics (PGI-2), Forschungszentrum Jülich, Jülich, Germany","correspondingAuthor":false,"prefix":"","firstName":"Markus","middleName":"","lastName":"Müller","suffix":""}],"badges":[],"createdAt":"2025-07-10 12:15:32","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7092911/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7092911/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-026-68533-x","type":"published","date":"2026-01-26T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":101390332,"identity":"02046cee-627c-4dda-8fb2-794abeae2c7c","added_by":"auto","created_at":"2026-01-29 08:11:17","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1053274,"visible":true,"origin":"","legend":"Article File","description":"","filename":"Main.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7092911/v1_covered_cf7e576f-ed9c-4b6e-9b22-11dfc78542c1.pdf"}],"financialInterests":"\u003cb\u003eYes\u003c/b\u003e there is potential Competing Interest.\nThomas Monz is connected to Alpine Quantum Technologies GmbH, a commercially oriented quantum computing company. 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Contemporary QEC schemes typically require mid-circuit measurements with feed-forward control, which are challenging for qubit control, often slow, and susceptible to relatively high error rates. In this work, we propose and experimentally demonstrate a universal toolbox of fault-tolerant logical operations without mid-circuit measurements on a trapped-ion quantum processor. We present modular logical state teleportation between two four-qubit error-detecting codes without measurements during algorithm execution. Moreover, we realize a fault-tolerant universal gate set on an eight-qubit error-detecting code hosting three logical qubits, based on state injection, which can be executed by coherent gate operations only. We apply this toolbox to experimentally realize Grover's quantum search algorithm fault-tolerantly on three logical qubits encoded in eight physical qubits, with the implementation displaying clear identification of the desired solution states. 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